The mooring systems which are conventionally used with offshore oil rigs and platforms typically consist essentially of a wire clamped around an aircraft tire and/or shackled to a padeye. This wire is used to secured the mooring lines for the oil rigs and platforms . It has been my experience that over a relatively short period of time, these wires cut through the tire, bringing the whole rigging down. The lines and the tires consistently fail because of the surge motion of the associated vessels caused by wind and seas. In many instances, the loose rigging then gets fouled up in the shafts and screws of the vessel. The problems caused by these failures are enormous. Crew members have been injured and even killed by the fallen rigging and other consequences of mooring line failure. In addition, the sucking of the lines and/or tires into the screws and shafts of a supply or utility vessel can cost thousands of dollars (and, in my experience, has collectively cost millions of dollars) on vessel down time and repair. Further, the cost of a coil of mooring line of the type used on offshore oil rigs and ocean going towing vessels can itself easily exceed twenty thousand dollars.
A further huge and costly problem is that produced when the shock line of an ocean towing vessel breaks on the high seas. The consequences of a runaway petroleum barge running aground, or millions of dollars of cargo containers washing up at a remote location, can be catastrophic, both, economically, for boat and cargo owners and insurance companies alike, and, environmentally, particularly where there is an attendant oil spill. The shock lines used in these ocean going towing operations are made of nylon, normally have a diameter of about six to eight inches and typically come in 50, 100 and 150 lengths. When a nylon line stretches to one half of its length, the line will break, and will snap back to its original diameter. It will be appreciated that when one of these large diameter lines hits a crewman, there is usually little hope for survival. This dire situation is compounded by the fact that even if the crewman survives the initial incident, medical help must be flown out to the vessel and this, of course, reduces the chances of survival. Although such nylon lines are, of course, very strong, such factors as a failure of the tugboat crew to keep the towing wires and bridles greased, and the inevitable weathering of the shock lines, have all too often meant that a sudden surge, brought on by a huge sea or wind, has caused the line to snap, thus unleashing the possibilities of all of the unfortunate consequences that can potentially occur (including that of a 400,000 barrel oil barge running aground).
In addition to the other disadvantages described above, such shock lines can take four to five hours to unreel from a storage drum or reel on deck and require substantial storage space.